Dredging is a common operation wherein bottom materials, such as mud, sand and sediment, are removed from a waterway. Dredging can be performed for a number of reasons, such as increasing the depth of a harbor, channel or river to permit the safe passage of deep-draft vessels. Dredging can also be performed to permit the recovery of minerals or other valuable raw materials from areas that are underwater. In addition, dredging can be used to remove contaminated sediments from polluted harbors and rivers as part of a remedial clean-up operation.
Typically, dredging is performed by means of a crane operated bucket that is repeatedly raised and lowered into the water to scoop up bottom materials and bring them to the surface for removal. Other forms of dredging can be accomplished using pumps to remove bottom materials and pump them to the surface in a water-based slurry. Whatever the purpose or method, dredging operations inherently create the problem of what to do with the “spoils” created as mud, sand, sediment and other materials are removed from the bottom and brought to the surface.
Typically, water makes up a large part of the dredge spoils. The goal of dredging, however, is not to remove water from the waterway but, rather, solids from the bottom. The water is brought up as an unavoidable consequence inherent in the dredging operation itself. Unless contaminated by the dredging operation itself, it is most economical and practical to return the water component of the dredge spoils to the waterway after removing the solid components. This is most economical and practical if it can be carried out on site without necessitating transportation of the spoils over long distances. A variety of techniques have, therefore, been developed for dewatering dredge spoils in dredging operations. Although effective, such techniques have left room for improvement in terms of simplicity, efficiency and economy.